In cellular networks, performance of a radio link to a device connected to the cellular network may be optimized by adaptation of a modulation and coding scheme (MCS) utilized on the radio link. For example, in the LTE (Long Term Evolution) radio technology specified by 3GPP (3rd Generation Partnership Project), modulation schemes ranging from QPSK (Quadrature Phase Shift Keying) to 256QAM (8th order Quadrature Amplitude Modulation) may be selected depending on channel quality. In this way, a throughput in terms of a number of bits per transmitted data symbol may be maximized on the given link.
Irrespective of a general trend to increased performance on the radio link, also Machine Type Communication (MTC) is gaining increasing attention.
In the case of MTC, autonomously operating devices such as sensors or actuators, are connected via the cellular network and typically operate without interaction of a user.
For MTC devices, low power consumption is an important aspect for ensuring long battery life. To achieve such low power consumption, various measures may be considered. For example, in 3GPP TR 36.888 V12.0.0 (2013 June), it is suggested to limit a transport block size or modulation order on radio links to MTC devices. It is also mentioned that BPSK (Binary Phase Shift Keying) could be utilized.
However, introducing a further modulation scheme into the existing LTE radio technology is a challenging task since the LTE radio technology was designed to support modulation schemes ranging from QPSK up to 256QAM, and a newly introduced modulation scheme should not adversely affect compatibility with existing LTE devices. For example, in the LTE radio technology, settings with respect to the modulation and coding scheme are identified through a 5-bit MCS index, referred to as IMCS, and a table in which modulation order and transport block size index are specified for each MCS index value, as specified in 3GPP TS 36.213 V12.4.0 (2014 December). Due to the limitation of the MCS index to 5 bits, also the size of the table is limited and cannot be extended beyond the existing 32 entries. Further, also a complete replacement of the table adds undesirable complexity because the existing version of the table would typically need to be maintained as well for compatibility reasons.
Accordingly, there is a need for techniques which allow for efficiently increasing the flexibility of a cellular network with respect to the selection of modulation schemes.